Benzaldehydes having ortho halogen substituents or having a total of up to five halogen substituents are extensively described in the chemical literature as starting materials for the synthesis of active substances (e.g. EP-A-0 174 131, EP-A-0 271 240, EP-A-0 289 942, FR-A-1 514 517, U.S. Pat. No. 3,856,504, U.S. Pat. No. 3,982,020, U.S. Pat. No. 4,902,814) or generally as an intermediate (DE-A 3310 953). Aldehydes which have a chlorine, bromine or iodine substituent in one ortho position and a fluorine substituent in the other, are known in the form of 2-chloro-6-fluorobenzaldehyde, 2-bromo-6-fluorobenzaldehyde and 2-fluoro-6-iodobenzaldehyde. However, there is a need for compounds having a plurality of fluorine substituents and additional functionalities, since fluorination or a different degree of fluorination very often enhances the activity of agrochemicals or pharmaceuticals by changing the lipophilicity and/or dipole moment (Kanie et al., Bull. Chem. Soc. Jpn. 2000, 73, 471).
Benzaldehydes having a plurality of fluorine substituents, one of which is ortho to the aldehyde function, and an ortho halogen substituent (which is not fluorine), are unknown, although some of these compounds can be constructed from generic formulations in the above mentioned references.